Preprocess CPU usage.

Things of note: Worker::GetCpuUsage() functionality was moved to
TimelineItemCpuData::PreprocessCpuUsage().

server/TracyTimelineDraw.hpp

@@ -56,6 +56,13 @@ struct MessagesDraw
     uint32_t num;
 };
 
+
+struct CpuUsageDraw
+{
+    int own;
+    int other;
+};
+
 }
 
 #endif